Arresting methanogenesis with bioelectrochemically generated hydrogen peroxide for producing volatile fatty acids

Anaerobic digestion (AD) is a promising and versatile environmental biotechnology platform for converting organic wastes to an energy-rich biogas for heating, electricity generation, and upgrading to produce renewable natural gas. AD has also shown great potential to convert organic wastes to volatile fatty acids (VFAs) which can serve as building blocks for the manufacturing of high-value products.

During the anaerobic digestion of organic wastes, acetogenic bacteria generate VFAs that also serve as intermediate compounds for biogas production by methanogenic bacteria. Thus, the inhibition of methanogens has emerged as a promising strategy for enhancing the production of VFAs while minimizing biogas generation during the anaerobic digestion of organic wastes.

The overarching goal of this project is to investigate the utilization of hydrogen peroxide generated from the bioelectrochemical (BEC) conversion of organic wastes to inhibit the growth and activity of methanogenic bacteria in anaerobic digesters. To advance this goal, the Principal Investigator proposes to explore the design, evaluation, and validation of an integrated and efficient AD-BEC-membrane separation system that could convert organic wastes to VFAs with high product yield and purity.

The successful completion of this project will benefit society through the generation of fundamental knowledge to advance the sustainable conversion of organic wastes to high value products. Additional benefits to society will be achieved through outreach and educational activities including the mentoring of one graduate and two undergraduate students at Washington University in St. Louis.

Anaerobic digestion (AD) has shown great potential to contribute to the decarbonization of the chemical industry via the conversion of organic wastes to high-value chemicals such as volatile fatty acids (VFAs) which can serve as building blocks for the manufacturing of industrially relevant products. However, the ability to tune and control the product spectrum of anaerobic digesters to maximize the yield and purity of VFAs remains a critical and unresolved challenge.

The goal of this project is to explore an innovative approach to maximize the yield and purity of VFA production during the anaerobic digestion of organic wastes. To advance this goal, the Principal Investigator (PI) proposes to explore the utilization of in-situ generated hydrogen peroxide to inhibit the growth and activity of methanogenic bacteria which utilize VFAs as intermediate compounds to generate biogas in anaerobic digesters.

The proposed inhibition of methanogenesis will be investigated within an integrated VFA production system consisting of an anaerobic digestor for product generation, a membrane separation module for product purification/concentration, and a bioelectrochemical reactor for in-situ H2O2 generation using organic wastes. The specific objectives of the research are to: (1) Advance the fundamental understanding of the mechanisms of methanogenesis inhibition by H2O2 during AD through integrated experimental and modeling studies; (2) Evaluate thermal or electrically driven membrane systems for the effective separation and purification of VFAs generated during AD; and (3) Explore the establishment of a translational scale system as a platform for performing a techno-economic assessment of the proposed integrated VFA production system.

The successful completion of this research has the potential for transformative impact through the generation of new fundamental knowledge to advance the development and implementation of more efficient and cost-effective technologies to recover valuable chemicals and compounds from organic wastes. To implement the education and outreach activities of the project, the PI plans to integrate the findings from this research into existing undergraduate/graduate courses at Washington University in St.

Louis to provide students with hands-on training (including lab sessions) on environmental resource recovery. In addition, the PI plans to explore the development and implementation of a Research Experience for Teachers (RET) program in collaboration with local high schools in St. Louis.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.